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/**
 * Copyright 2014 Netflix, Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package rx.functions;

public class Functions {

    /**
     * Converts a {@link Func0} to a {@link FuncN} to allow heterogeneous handling of functions with different
     * arities.
     * 
     * @param f
     *          the {@code Func0} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static  FuncN fromFunc(final Func0 f) {
        return new FuncN() {

            @Override
            public R call(Object... args) {
                if (args.length != 0) {
                    throw new RuntimeException("Func0 expecting 0 arguments.");
                }
                return f.call();
            }

        };
    }

    /**
     * Converts a {@link Func1} to a {@link FuncN} to allow heterogeneous handling of functions with different
     * arities.
     * 
     * @param f
     *          the {@code Func1} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static  FuncN fromFunc(final Func1 f) {
        return new FuncN() {

            @SuppressWarnings("unchecked")
            @Override
            public R call(Object... args) {
                if (args.length != 1) {
                    throw new RuntimeException("Func1 expecting 1 argument.");
                }
                return f.call((T0) args[0]);
            }

        };
    }

    /**
     * Converts a {@link Func2} to a {@link FuncN} to allow heterogeneous handling of functions with different
     * arities.
     * 
     * @param f
     *          the {@code Func2} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static  FuncN fromFunc(final Func2 f) {
        return new FuncN() {

            @SuppressWarnings("unchecked")
            @Override
            public R call(Object... args) {
                if (args.length != 2) {
                    throw new RuntimeException("Func2 expecting 2 arguments.");
                }
                return f.call((T0) args[0], (T1) args[1]);
            }

        };
    }

    /**
     * Converts a {@link Func3} to a {@link FuncN} to allow heterogeneous handling of functions with different
     * arities.
     * 
     * @param f
     *          the {@code Func3} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static  FuncN fromFunc(final Func3 f) {
        return new FuncN() {

            @SuppressWarnings("unchecked")
            @Override
            public R call(Object... args) {
                if (args.length != 3) {
                    throw new RuntimeException("Func3 expecting 3 arguments.");
                }
                return f.call((T0) args[0], (T1) args[1], (T2) args[2]);
            }

        };
    }

    /**
     * Converts a {@link Func4} to a {@link FuncN} to allow heterogeneous handling of functions with different
     * arities.
     * 
     * @param f
     *          the {@code Func4} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static  FuncN fromFunc(final Func4 f) {
        return new FuncN() {

            @SuppressWarnings("unchecked")
            @Override
            public R call(Object... args) {
                if (args.length != 4) {
                    throw new RuntimeException("Func4 expecting 4 arguments.");
                }
                return f.call((T0) args[0], (T1) args[1], (T2) args[2], (T3) args[3]);
            }

        };
    }

    /**
     * Converts a {@link Func5} to a {@link FuncN} to allow heterogeneous handling of functions with different
     * arities.
     * 
     * @param f
     *          the {@code Func5} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static  FuncN fromFunc(final Func5 f) {
        return new FuncN() {

            @SuppressWarnings("unchecked")
            @Override
            public R call(Object... args) {
                if (args.length != 5) {
                    throw new RuntimeException("Func5 expecting 5 arguments.");
                }
                return f.call((T0) args[0], (T1) args[1], (T2) args[2], (T3) args[3], (T4) args[4]);
            }

        };
    }

    /**
     * Converts a {@link Func6} to a {@link FuncN} to allow heterogeneous handling of functions with different
     * arities.
     * 
     * @param f
     *          the {@code Func6} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static  FuncN fromFunc(final Func6 f) {
        return new FuncN() {

            @SuppressWarnings("unchecked")
            @Override
            public R call(Object... args) {
                if (args.length != 6) {
                    throw new RuntimeException("Func6 expecting 6 arguments.");
                }
                return f.call((T0) args[0], (T1) args[1], (T2) args[2], (T3) args[3], (T4) args[4], (T5) args[5]);
            }

        };
    }

    /**
     * Converts a {@link Func7} to a {@link FuncN} to allow heterogeneous handling of functions with different
     * arities.
     * 
     * @param f
     *          the {@code Func7} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static  FuncN fromFunc(final Func7 f) {
        return new FuncN() {

            @SuppressWarnings("unchecked")
            @Override
            public R call(Object... args) {
                if (args.length != 7) {
                    throw new RuntimeException("Func7 expecting 7 arguments.");
                }
                return f.call((T0) args[0], (T1) args[1], (T2) args[2], (T3) args[3], (T4) args[4], (T5) args[5], (T6) args[6]);
            }

        };
    }

    /**
     * Converts a {@link Func8} to a {@link FuncN} to allow heterogeneous handling of functions with different
     * arities.
     * 
     * @param f
     *          the {@code Func8} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static  FuncN fromFunc(final Func8 f) {
        return new FuncN() {

            @SuppressWarnings("unchecked")
            @Override
            public R call(Object... args) {
                if (args.length != 8) {
                    throw new RuntimeException("Func8 expecting 8 arguments.");
                }
                return f.call((T0) args[0], (T1) args[1], (T2) args[2], (T3) args[3], (T4) args[4], (T5) args[5], (T6) args[6], (T7) args[7]);
            }

        };
    }

    /**
     * Converts a {@link Func9} to a {@link FuncN} to allow heterogeneous handling of functions with different
     * arities.
     * 
     * @param f
     *          the {@code Func9} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static  FuncN fromFunc(final Func9 f) {
        return new FuncN() {

            @SuppressWarnings("unchecked")
            @Override
            public R call(Object... args) {
                if (args.length != 9) {
                    throw new RuntimeException("Func9 expecting 9 arguments.");
                }
                return f.call((T0) args[0], (T1) args[1], (T2) args[2], (T3) args[3], (T4) args[4], (T5) args[5], (T6) args[6], (T7) args[7], (T8) args[8]);
            }

        };
    }

    /**
     * Converts an {@link Action0} to a {@link FuncN} to allow heterogeneous handling of functions with
     * different arities.
     * 
     * @param f
     *          the {@code Action0} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static FuncN fromAction(final Action0 f) {
        return new FuncN() {

            @Override
            public Void call(Object... args) {
                if (args.length != 0) {
                    throw new RuntimeException("Action0 expecting 0 arguments.");
                }
                f.call();
                return null;
            }

        };
    }

    /**
     * Converts an {@link Action1} to a {@link FuncN} to allow heterogeneous handling of functions with
     * different arities.
     * 
     * @param f
     *          the {@code Action1} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static  FuncN fromAction(final Action1 f) {
        return new FuncN() {

            @SuppressWarnings("unchecked")
            @Override
            public Void call(Object... args) {
                if (args.length != 1) {
                    throw new RuntimeException("Action1 expecting 1 argument.");
                }
                f.call((T0) args[0]);
                return null;
            }

        };
    }

    /**
     * Converts an {@link Action2} to a {@link FuncN} to allow heterogeneous handling of functions with
     * different arities.
     * 
     * @param f
     *          the {@code Action2} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static  FuncN fromAction(final Action2 f) {
        return new FuncN() {

            @SuppressWarnings("unchecked")
            @Override
            public Void call(Object... args) {
                if (args.length != 2) {
                    throw new RuntimeException("Action3 expecting 2 arguments.");
                }
                f.call((T0) args[0], (T1) args[1]);
                return null;
            }

        };
    }

    /**
     * Converts an {@link Action3} to a {@link FuncN} to allow heterogeneous handling of functions with
     * different arities.
     * 
     * @param f
     *          the {@code Action3} to convert
     * @return a {@link FuncN} representation of {@code f}
     */
    public static  FuncN fromAction(final Action3 f) {
        return new FuncN() {

            @SuppressWarnings("unchecked")
            @Override
            public Void call(Object... args) {
                if (args.length != 3) {
                    throw new RuntimeException("Action3 expecting 3 arguments.");
                }
                f.call((T0) args[0], (T1) args[1], (T2) args[2]);
                return null;
            }

        };
    }

    /**
     * Constructs a predicate that returns true for each input for which the source predicate returns false, and
     * vice versa.
     * 
     * @param predicate
     *            the source predicate to negate
     * @return a function that returns a Boolean that represents an inversion of the logical effect of
     *         {@code predicate}
     */
    public static  Func1 not(Func1 predicate) {
        return new Not(predicate);
    }

    /**
     * Returns a function that always returns {@code true}.
     *
     * @return a {@link Func1} that accepts an Object and returns the Boolean {@code true}
     */
    public static  Func1 alwaysTrue() {
        return AlwaysTrue.INSTANCE;
    }

    /**
     * Returns a function that always returns {@code false}.
     *
     * @return a {@link Func1} that accepts an Object and returns the Boolean {@code false}
     */
    public static  Func1 alwaysFalse() {
        return AlwaysFalse.INSTANCE;
    }

    /**
     * Returns a function that always returns the Object it is passed.
     *
     * @return a {@link Func1} that accepts an Object and returns the same Object
     */
    public static  Func1 identity() {
        return new Func1() {
            @Override
            public T call(T o) {
                return o;
            }
        };
    }

    private enum AlwaysTrue implements Func1 {
        INSTANCE;

        @Override
        public Boolean call(Object o) {
            return true;
        }
    }

    private enum AlwaysFalse implements Func1 {
        INSTANCE;

        @Override
        public Boolean call(Object o) {
            return false;
        }
    }

    /**
     * Returns a function that merely returns {@code null}, without side effects.
     *
     * @return a function that returns {@code null}
     */
    @SuppressWarnings("unchecked")
    public static  NullFunction returnNull() {
        return (NullFunction) NULL_FUNCTION;
    }

    @SuppressWarnings("rawtypes")
    private static final NullFunction NULL_FUNCTION = new NullFunction();

    private static final class NullFunction implements
            Func0,
            Func1,
            Func2,
            Func3,
            Func4,
            Func5,
            Func6,
            Func7,
            Func8,
            Func9,
            FuncN {
        @Override
        public R call() {
            return null;
        }

        @Override
        public R call(T0 t1) {
            return null;
        }

        @Override
        public R call(T0 t1, T1 t2) {
            return null;
        }

        @Override
        public R call(T0 t1, T1 t2, T2 t3) {
            return null;
        }

        @Override
        public R call(T0 t1, T1 t2, T2 t3, T3 t4) {
            return null;
        }

        @Override
        public R call(T0 t1, T1 t2, T2 t3, T3 t4, T4 t5) {
            return null;
        }

        @Override
        public R call(T0 t1, T1 t2, T2 t3, T3 t4, T4 t5, T5 t6) {
            return null;
        }

        @Override
        public R call(T0 t1, T1 t2, T2 t3, T3 t4, T4 t5, T5 t6, T6 t7) {
            return null;
        }

        @Override
        public R call(T0 t1, T1 t2, T2 t3, T3 t4, T4 t5, T5 t6, T6 t7, T7 t8) {
            return null;
        }

        @Override
        public R call(T0 t1, T1 t2, T2 t3, T3 t4, T4 t5, T5 t6, T6 t7, T7 t8, T8 t9) {
            return null;
        }

        @Override
        public R call(Object... args) {
            return null;
        }
    }
}




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